Carbon nanotube induced structural and physical property transitions of syndiotacticpolypropylene

Abstract

In this paper we have studied the effect of increasing carbon multi-wallednanotube (CNT) concentration in composites of syndiotactic polypropylene (sPP)having the same crystalline form but different morphologies. The attention wasfocused on the form I of sPP with different degrees of perfection (in terms ofpercentages of chains in helical conformation, crystal dimensions and crystallinity)obtained using two different quenching temperatures from the melt, i.e. 25 and100 °C. We observed a decreasing effect of the crystallization temperature on increasing thenanotube content up to the samples with 10% of CNT, that show a very similar structuralorganization independent of the undercooling. Only the amorphous phase turnsout more relaxed in the samples crystallized at the highest temperature. Eitherthe thermal or the mechanical properties are improved on increasing the CNTcontent in both series of samples. The electrical conductivity increases in a similarmanner in both series of samples and between 1 and 3 wt% it shows a sizablestep of about eight orders of magnitude, a phenomenon that can be regarded asthe onset of a percolating structure for which charge transport may take place.